Was on a 4 lane highway on a long upgrade when i heard a snap like a driveshaft ujoint had broke i thought thats what happened cause motor would rev up but it wouldent move anymore.. No sliping before this just a loud snap.. Someone ask me to rev the engine & try to put it back up into Park to listin to any sounds or movements.. Nothing at all but it went in with no problems.. Not sure if its the Transmission Or Transfercase is bad????? PLEASE HELP

Could be either of them. When you are trying to drive it, does the driveshaft turn? Does the speedometer move? Do you hear any grinding or clattering when trying to move it now? You're looking at a few possible situations here.

#1 you blew the rear end or a component within it. The driveshaft will turn if this is the case.

#2 the transfer case is blown. Not sure off the top of my head if the speed sensor is in the t-case or the trans on this one so look for it. If its on the trans, and you get a reading on your speedometer, then you have a bad t-case.

#3 you blew the trans up. Check for fluid level being correct. If the mainshaft or the pump in the trans is what made the noise, you'll be able to unhook one of your transmission cooler hoses and not see fluid pumping out when the engine is running. Its not a definitive diagnosis, as many other things can fail internally in a transmission and leave the pump operating, but its a place to start to narrow this down without needing a lot of tools or taking a lot of time to do.